Epidemiological and virological studies on outbreaks of acute gastroenteritis associated with rotavirus in primary schools in Osaka.

There have been three recent outbreaks of acute gastroenteritis in primary schools in Osaka prefecture caused by rotavirus: one in a school (TA) in April, 1974 and two in two other schools (TE and K) in May 1975. The morbidity from the disease was 2.4--15.8% for all age groups in the schools, and 20.1--34.1% for a certain age group. The disease lasted for 4 (K) to 14 days (TE). The first cases in schools TA and TE were followed by successive cases. The main clinical symptoms were higher frequencies of diarrhea (68--71.4%) and fever (78%) than in winter vomiting disease. There was no difference in the incidences of the disease in boys and girls. From observation on the disease in individual families, the incubation period seemed to be 3 days. Using paired sera and Neonatal Calf Diarrhea Virus (NCDV) as antigen, positive seroconversion was demonstrated by the complement fixation test and marked seroconversion by the indirect fluorescent antibody technique. With these techniques, specific antibody to NCDV was detectable in the sera from an early stage of illness. Rotavirus was found on electron microscopic examination of some fecal specimens of patients in TA, but not in those of patients in TE or K, although adenovirus was isolated from one patient. A serological survey of healthy children aged 0 to 12 showed that rotavirus is a common virus in Osaka.